The invention is directed to a tube furnace for the performance gas reactions, especially for the production of hydrocyanic acid according to the BMA process (hydrocyanic acid-methane-ammonia process), in which the individual structural parts in consideration of energy and industrial safety aspects are arranged in a special way to each other and besides each other. The previously known type furnaces for the performance gas reactions, especially at temperatures above 900.degree. C., for example at temperatures between 1000.degree. C. and 1500.degree. C. consist of a series of parallel connected heating chambers which are mounted with freely suspended ceramic tubes or tube assemblies. Each of these chambers is heated separately. The flue gas discharge takes place via a separate branch channel which is joined via transition pieces with the individual chambers. The vertically arranged ceramic tubes, whose inside represents the actual reaction space, are supplied with the necessary heat for the reaction through the tube walls so that the heating chambers accordingly must be lined with a temperature resistant material. The heat is produced by gas or oil burners. The combustion air is heated recuperatively. The burners, of which 2 elements are needed per chamber, are arranged in the lower region of the chamber in order that the entire length of the reaction tubes as far as possible can be brought to the required reaction temperature. The heat of the departing flue gases can be used for preheating the air and/or for producing the steam.
It is possible with several furnaces, to connect every two furnaces to a common branch channel which then is arranged between these two furnaces and via a collection channel with the help of an induced draft blower to use the heat content of the flue gas in a waste-heat boiler for the production of steam.
The recuperators for the preheating of the combustion air are in each case arranged between two chambers and are heated simultaneously with the reaction tubes (German Pat. No. 1,041,476 and related Endter U.S. Pat. No. 2,987,382. The entire disclosure of Endter is hereby incorporated by reference and relied upon).
However, a disadvantage of great importance in this is that there are needed two burners per heating chamber so that when there are present a large number of heating chambers there must be manipulated and adjusted an even larger number of burners. This is not without problems since the combustion process and therewith the control of the reaction temperature is greatly influenced by the manner of travel of the burner. Among others, this is especially made difficult by the fact that freely suspended reaction tubes can only be incompletely sealed off compared to the lower furnace covering.
A further disadvantage of this known furnace is its quite large outer surface which leads to energy losses.
These disadvantages are avoided by the furnace of the invention. Also, through a different arrangement of the recuperators, there is produced a higher preheating of the combustion air and therewith a better cooling of the flue gases.